In the steering device that the telescopic position or the tilting position of the steering wheel is adjustable, after the telescopic position or the tilting position of the steering wheel is adjusted, a column is firmly clamped to a vehicle body attaching bracket so that the steering wheel does not move from that position.
As a steering device in which a telescopic position is adjustable and an outer column is clamped to an inner column, there is a steering device disclosed in Patent Document 1. In the steering device disclosed in the Patent Document 1, since the inner column is strongly fastened to the outer column, a position offsetting from the axis of the outer column is fastened.
FIG. 7 is an enlarged longitudinally sectional view showing a conventional steering device in which a position offsetting from the axis of an outer column is fastened. As shown in FIG. 7, in the hollow and cylindrical outer column 1, a steering shaft 4 is supported to freely rotate. To the steering shaft 4 in the rear side of a vehicle body (a front side in the direction intersecting at right angles to the surface of a sheet of FIG. 7), a steering wheel not shown in the drawing is attached.
To a cylindrical inner peripheral surface 15B formed in the outer column 1 in the front side of the vehicle body (an interior side in the direction intersecting at right angles to the surface of the sheet of FIG. 7), an inner column is internally fitted. The outer column 1 is attached to the vehicle body 6 by a vehicle body attaching bracket (an upper bracket) 3.
A part of the inner column 2 in the front side of the vehicle body is pivotally supported by the vehicle body 6 through a tilting central shaft not shown in the drawing. On the upper part of the vehicle body attaching bracket 3, a pair of right and left flange parts 31A and 31B for attaching the vehicle body attaching bracket 3 to the vehicle body 6 is formed. The flange parts 31A and 31B are fastened to the vehicle body 6 by bolts 312A and 312B and abutting surfaces 311A and 311B on the upper surface of the flange parts 31A and 31B abut on the vehicle body 6 and are fixed thereto. In the flange parts 31A and 31B, a pair of right and left side plates 32A and 32B are bent in L shapes and extend downwardly from the flange parts 31A and 31B.
In the lower part of the outer column 1, clamp parts 11A and 11B are integrally formed. In the lower surface of the outer column 1 and the lower surfaces of the clamp parts 11A and 11B, a slit 13 is formed so as to pass through from the outer peripheral surface 15A to the inner peripheral surface 15B of the outer column 1. The slit 13 is formed over the entire length of a telescopic position adjusting range of the outer column 1.
Between inner surfaces 321A and 321B of the side plates 32A and 32B of the vehicle body attaching bracket 3, side surfaces of the clamp parts 11A and 11B are held so as to move telescopically and tilt.
In the clamp parts 11A and 11B, telescopic long grooves 12A and 12B elongating in the axial direction of the outer column 1 are formed in the lower part of the axis of the outer column 1. Further, a fastening rod 34 is inserted into tilting long grooves 33A and 33B formed in the side plates 32A and 32B and the telescopic long grooves 12A and 12B from the right side of FIG. 7 (intersecting at right angles to the axis of the outer column 1).
In the right side of the fastening rod 34, a disk shaped head part (a fastening member) 341 is formed. In the outer periphery of the head part 341, chamfered parts 342 and 342 are formed in parallel. The chamfered part 342 is internally fitted to the tilting long groove 33B to prevent the fastening rod 34 from rotating relative to the vehicle body attaching bracket 3 and to achieve tilt movement of the fastening rod 34 along the long tilting groove 33B.
An end face 343 of the head part 341 abuts on an outer surface 322B of the side plate 32B. In a left side of the fastening rod 34, a male screw 344 is formed. To the male screw 344, a cylindrical nut (a fastening member) 35 is screwed. An end face 351 of the nut 35 abuts on an outer surface 322A of the side plate 32A. To the nut 35, an operating lever 36 is fixed through a washer 37 and a bolt 38.
Inside surfaces of the clamp parts 11A and 11B respectively, abutting surfaces 17A and 17B are formed in the vicinity of the axis of the fastening rod 34. The abutting surfaces 17A and 17B lightly abut on the inner surfaces 321A and 321B of the side plates 32A and 32B, even when the fastening rod 34 is unfastened. The abutting surfaces 17A and 17B can abut on the inner surfaces 321A and 321B of the side plates 32A and 32B over the entire length of the telescopic position adjusting range of the outer column 1.
The outer peripheral surface 15A of the outer column 1 has a space between the inner surfaces 321A and 321B of the side plates 32A and 32B and the outer peripheral surface 15A, even when the fastening rod 34 is fastened.
When swinging the operating lever 36, the nut 35 rotates so that the side plates 32A and 32B is fastened through the fastening rod 34 or a fastening state is released. That is, when the operating lever 36 is swung in a fastening direction, the nut 35 rotates and the end face 351 of the nut 35 moves to a right side of FIG. 7 and the fastening rod 34 moves to a left side of FIG. 7.
As a result, the end face 351 of the nut 35 fastens the outer surface 322A of the side plate 32A and the end face 343 of the head part 341 fastens the outer surface 322B of the side plate 32B. Thus, the inner surfaces 321A and 321B of the side plates 32A and 32B strongly press the abutting surfaces 17A and 17B in the vicinity of the axis of the fastening rod 34 to deform the clamp parts 11A and 11B toward the axis of the outer column 1 and narrow the width of the slit 13.
As a result, the diameter of the inner peripheral surface 15B of the outer column 1 is reduced to strongly fasten the outer column 1 to inner column 2. At the same time, the abutting surfaces 17A and 17B in the vicinity of the axis of the fastening rod 34 are strongly fastened by the inner surfaces 321A and 321B of the side plates 32A and 32B.
Accordingly, the axis of the outer column 1 is considered to be a fulcrum point, a center of the abutting parts of the abutting surfaces 17A and 17B in the vicinity of the axis of the fastening rod 34 and the inner surfaces 321A and 321B is considered to be a power point, and the clamp parts 11A and 11B are fastened by a moment proportional to a distance L2 between the fulcrum point and the power point. Therefore, the outer column 1 can be strongly pressed to the inner column 2.
However, the fastening position of the side plates 32A and 32B of the vehicle body attaching bracket 3 and the outer column 1 is located in the vicinity of the axis of the fastening rod 34 spaced downward from the axis of the outer column 1.
Accordingly, when a steering force is applied to the outer column 1 from the steering wheel, in a moment applied to the vehicle body attaching bracket 3 by this steering force, the abutting surfaces 311A and 311B of the flange parts 31A and 31B and the vehicle body 6 are considered to be a fulcrum point. Further, a center of the abutting parts of the abutting surfaces 17A and 17B in the vicinity of the axis of the fastening rod 34 and the inner surfaces 321A and 321B are considered to be a power point. A large force acts on the vehicle body attaching bracket 3 by a moment proportional to a distance L1 between the fulcrum point and the power point. Accordingly, a rightward and leftward supporting rigidity in FIG. 7 is low relative to the steering force applied to the outer column 1.
In order to improve the supporting rigidity of the vehicle body attaching bracket, the vehicle body attaching bracket may be reinforced, however, a problem arises that the cost of a material is high and a weight increases. Further, to improve the supporting rigidity of the vehicle body attaching bracket 3, the abutting surfaces 17A and 17B in the vicinity of the axis of the fastening rod 34 may be extended near the axis of the outer column 1. However, since there is a dimensional unevenness in production, the fastening position of the side plates 32A and 32B of the vehicle body attaching bracket 3 and the outer column 1 is limited to a part in the vicinity of the axis of the fastening rod 34. Thus, it is difficult to improve the supporting rigidity of the vehicle body attaching bracket 3.
In steering devices disclosed in Patent document 2 and Patent Document 3, a spacer made of a synthetic resin is interposed between inner surfaces of a vehicle body attaching bracket and both right and left side surfaces of an outer column to improve the supporting rigidity of the vehicle body attaching bracket. However, in the steering device disclosed in the Patent Document 2, since the number of parts is increased, a problem arises that the cost of the parts is high and the number of assembling processes is increased.
Patent Document 1: JP-A-2001-347953
Patent Document 2: JP-A-8-207787
Patent Document 3: JP-B-3,415,953